Formulate and solve using the Graphical Method

Wyoming Electric Corp. owns a steam-turbine power-generating plant. Because Wyoming is rich in coal deposits, the plant generates its steam from coal. This, however, may result in emission that does not meet the Environment Protection Agency (EPA) standards. EPA regulations limit sulfur dioxide discharge to 2000 parts per million per ton of coal burned per hour and smoke discharge from the plant stacks to 20 lb per hour. The Corp. receives two grades of pulverized coal: Cl and C2, for use in the steam plant. The two grades are usually mixed together before burning. For simplicity, it can be assumed that the amount of sulfur pollutant discharged (on parts per million) is weighted average of the proportion of each grade used in the mixture. The following data are based on consumption of 1 ton per hour of each of the two coal grades. Determine the optimal ratio for mixing the two local grades. Coal grade Sulfur discharge in parts per million Smoke discharge in lb per Steam generated in lb per per ton of coal burned ton per hour C1 C2 1800 2100 2.1 0.9 12000 9000